Meeting Abstract

In nearly all of Earth’s ecosystems, organisms are being forced to develop mechanisms that will increase their fitness (survival and reproduction) in response to global climate change. Studies of the physiological and behavioral responses of freshwater organisms to temperature and solar ultraviolet (UV) radiation are highly variable (species, conditions, extremes of stressors, etc). It is well known that UV can induce significant stress in some organisms, including direct DNA damage, reduced reproduction rates, and death. Organisms in freshwater systems such as lakes and ponds are faced with high levels of UV exposures due to the clear water, thus must develop mechanisms to cope with the stressors. It has been known that food quality and quantity impact the fitness of many organisms, including freshwater species. The fitness response to acute UV-A exposure was studied in model freshwater cladocerans. Daphnia pulicaria, D. lumholtzi, and D. dentifera were raised on different algal food sources (Selenastrum capricornutum and Scenedesmus sp.) and exposed to acute UV-A (320 – 400nm; 1000 uW cm-2). Some daphniids, including Ceriodaphnia dubia, had increased levels of survival and reproduction with increasing UV-A radiation if reared on specific food combinations. While others, including D. dentifera, were negatively effected by the variable food sources, compounding their sensitivity to UV-A. Analysis of food sources may provide a better understanding of how organisms can cope with environmental stressors (improved nutrition), despite the rapid changes that can occur in their habitats. These findings can be extended to other populations and should be taken in to consideration for climate change models.